The present invention relates to a regenerative brake device for a vehicle and to a method for regenerative braking of a vehicle.
Hybrid vehicles may be powered by a primary prime mover which may be a combustion engine, and by a secondary prime mover which may be an electrical machine. The electrical machine will be equipped with at least one battery to store electrical energy and with regulating equipment to regulate the flow of electrical energy between the battery and the electrical machine. The electrical machine may thus serve alternately as motor and generator, depending on the vehicle's operating state. When the vehicle is braked, the electrical machine generates electrical energy which is then stored in the battery. This is usually called regenerative braking, which means that the vehicle is braked by means of the electrical machine and the combustion engine. The stored electrical energy is subsequently used for operation of the vehicle.
Using a conventional clutch mechanism which disconnects the gearbox input shaft from the engine during gearchange processes in the gearbox involves disadvantages, e.g. warming of the clutch mechanism's discs, resulting in greater fuel consumption and in clutch disc wear. In addition, a conventional clutch mechanism is relatively heavy and expensive. It also occupies a relatively large amount of space in the vehicle.
Connecting the engine output shaft, the electrical machine's rotor and the gearbox input shaft to a planetary gear makes it possible to dispense with the conventional clutch mechanism. In regenerative braking of the vehicle, however, the planetary gear will cause the regenerative braking torque of the electrical machine to be reduced because the engine's braking torque on the planetary gear will not be sufficient. In particular, during powerful regenerative braking with the electrical machine the engine's speed will increase undesirably.
Specification US-A1-2009/0288895 refers basically to how a ring gear in a planetary gear connected to an engine can be locked in a housing which is stationary relative to the planetary gear in order to effect regenerative braking of a vehicle by means of an electrical machine. The engine can be disconnected from the planetary gear's ring gear.
The space available for the propulsion device in a vehicle is often limited. If the propulsion device comprises a plurality of components, e.g. a combustion engine, an electrical machine, a gearbox and a planetary gear, the configuration needs to be compact. If further components, e.g. a regenerative brake device, are involved, this makes it still more necessary for the components of the propulsion device to be of compact configuration.
The components of the propulsion device are also required to be of high reliability and high operational safety.